The present invention relates to apparatus for the continuous separation of solid particles and gas, for example a mixture of fibrous material and steam. More particularly, the present invention relates to such apparatus comprising a housing with a substantially circular cross-section, a rotary rotor provided with carriers in the housing, a tangential inlet connected to the housing for a mixture of particle material and gas, and separate outlets for particles and gas, respectively.
During the manufacture of mechanized pulp from fibrous material in a refiner, large amounts of steam are simultaneously formed, as the fibrous material is defibered and refined to pulp. From the refiner a mixture of fibrous material and steam is transported to a device for separating the steam from the fibrous material. The steam is recovered for use in other locations in the process, and the fibrous material is advanced to subsequent process steps. The steam separation normally takes place in a cyclone, where the fibrous material/steam is supplied tangentially to a cylindrical container. The fibrous material, due to the effect of centrifugal force moves along the container wall downwardly, and is fed out through a conical tapering portion at the same time as the steam is discharged upwardly in the container. Such a cyclone can function well when the material is dry, but due to the fact that the fibrous material is often moist and includes sticky extractive matter, such as resins and the like,problems arise with non-uniform discharge and clogging of the cyclone. These problems can be overcome to some extent by placing a rotary helical transport means adjacent the cyclone wall in order to feed the material downwardly to the outlet during rotation. Such a transport means, however, disturbs the cyclone effect, and it has often even been found that the transport means is insufficient, and therefore does not entirely prevent the formation of fibrous deposits in the cyclone. The cyclone, instead, is overdimensioned in order to operate satisfactorily in spite of these fibrous deposits. This implies, however, increased costs for the equipment. Another problem with this type of cyclone is that it has a relatively poor separation effect during steam separation according to the above discussion.
One object of the present invention is to provide a separation device which eliminates the aforesaid problems. Such a device would thus avoid such fibrous deposits, and the separation effect can be improved without having to overdimension the device. The dimensions of such a device, instead, can be reduced in relation to a conventional cyclone with the same capacity. Such a device, futhermore, can be used for particulate material with a dry matter content down to about 20%.
These and other objects have now been realized by the discovery of apparatus for continuously separating a stream of solid particles in a gas comprising a housing having a substantially circular cross-sectional shape, and including a tangential inlet for the stream of solid particles in a gas, a first outlet for the solid particles and a second outlet for the gas, a rotor rotatably mounted within the housing for rotation therein, the rotor including a plurality of carriers thereabout, the tangential inlet and the first outlet being disposed on the periphery of the housing spaced from each other in the circumferential direction, and airtight discharge means associated with the first outlet, the second outlet being located centrally in the housing. In a preferred embodiment, the rotor comprises a circular disk, the plurality of carriers being disposed on the periphery of the circular disk. Preferably, the circular disk includes a plurality of openings disposed radially within the plurality of carriers.
The apparatus according to the present invention is designed for tangential supply of particulate material/gas to the periphery of the housing where the rotor provided with carriers rotates in the same direction as the supply of particulate material/gas. The rotational speed is higher, and preferably 10% to 20% higher, than the supply speed for the stream of particulate material/gas. Separate outlets for the particulate material and gas, respectively, are provided in the housing. The particle outlet is located at the periphery of the housing spaced from the inlet, while the gas outlet is located centrally. In this manner, the particulate material, by the influence of centrifugal force, will be moved to and out through the particle outlet, and at the same time the gas will flow out through the central outlet. By connecting the particle outlet to an air-tight discharge means gas is prevented from following along with the particle material, at the same time as particles are prevented from following along with the gas through the gas outlet by means of the centrifugal force thereof. In this way substantially 100% separation can be obtained.
A device according to the present invention can be used in such positions where cyclones are normally employed. Examples of fields of application for this apparatus are the cleaning of gas, where the gas device is coupled in an existing steam line. This apparatus can also be used during the manufacture of mechanical pulp in several steps by placing it between the refiners of the first and second step in order to separate steam from the first step, in connection with the feed-in screw to the second step. This apparatus can also be used for separating gas flowing rearwardly through the feed-in screw in a refiner.